Bighorn River (Wyoming)

The Bighorn River in Wyoming begins at one of the most poetically named landmarks in Western fly fishing: the Wedding of the Waters. Here, five miles south of Thermopolis, the Wind River officially becomes the Bighorn River as it emerges from the dramatic Wind River Canyon. What follows is approximately 14 miles of exceptional trout water flowing through and below the town of Thermopolis, home to the world's largest mineral hot spring at Hot Springs State Park.

This Wyoming section of the Bighorn should not be confused with its more famous downstream cousin, the Bighorn River tailwater below Yellowtail Dam in Montana, which is a separate and distinct fishery 90 miles to the north. The Wyoming Bighorn through Thermopolis is a different character entirely: a classic Western dry-fly stream with long stretches of slow, clear water holding large trout that feed eagerly on the surface.

Wyoming Game & Fish Department surveys consistently document over 3,000 trout per mile through the Thermopolis section, with a mix of rainbow, brown, and Yellowstone cutthroat trout averaging 16 to 18 inches. Fish over 20 inches are common, and trophy trout exceeding 25 inches are caught each season. The warm mineral springs that feed the river through Thermopolis elevate water temperatures slightly, contributing to exceptional insect production and year-round feeding activity.

The river's character is gentle and inviting: wide, slow-moving water with a gravel and cobble bottom that is easily waded. Long glides, gentle riffles, and deep pools against cottonwood-lined banks create classic dry-fly water where anglers can sight-fish to rising trout. The consistent hatches of midges, BWOs, Tricos, PMDs, and caddisflies support surface feeding for much of the year, making this a paradise for anglers who prefer fishing with a floating fly.

Wind River Canyon upstream of the Wedding of the Waters adds another dimension to the fishery. This spectacular limestone canyon, carved by the river over millions of years, holds good populations of brown and rainbow trout in a remote, scenic setting. Highway 20 parallels the river through the canyon, providing roadside access to productive pools and runs. The canyon section is less productive than the Thermopolis reach but offers dramatic scenery and solitude.

The Bighorn River through Thermopolis occupies a unique niche among Western trout rivers. The warm mineral hot springs that feed the river, most notably the Big Spring in Hot Springs State Park, which produces 2,575,440 gallons per day at a constant 135 degrees Fahrenheit, elevate water temperatures above what would be expected for a river at this latitude and elevation. The mineral content of these springs also enriches the water with calcium carbonate and other dissolved minerals that promote aquatic insect production. The result is a river with the biological productivity of a tailwater but the aesthetics and character of a freestone stream.

Water clarity is excellent year-round, typically 4 to 8 feet of visibility. The river maintains relatively stable flows because the Wind River Canyon upstream acts as a natural moderating influence, and the warm springs provide a consistent base flow. The substrate through the Thermopolis section is predominantly clean gravel and small cobble, ideal for both aquatic insects and trout spawning. Aquatic vegetation is moderate, supporting healthy populations of midges, mayflies, caddisflies, scuds, and crayfish.

The Wind River Canyon upstream adds a different water character: colder, faster, and more nutrient-poor than the Thermopolis reach. The canyon's limestone walls contribute some alkalinity to the water, but insect densities are lower than the warm-spring-enriched section below. Water temperatures in the canyon follow a more typical freestone pattern, warming in summer and cooling in winter without the moderating influence of the hot springs.